Commonly owned U.S. Pat. Nos. 6,305,131; 6,223,473; 5,396,742; 5,301,479; and 5,285,617, all of which are expressly incorporated by reference herein, disclose various hazardous material storage buildings and features thereof.
Hazardous materials, such as chemicals or waste in either a solid or liquid form, are frequently placed in 55-gallon cylindrical barrels. These drums are typically further stored in a storage facility. Such drums, however, can easily develop leaks over time. Accordingly, these barrels must be kept in a facility that has suitable safety features such as proper venting, fire and explosion protection, leakage protection with a sump built into the floor, and leakage detection.
Because it is preferable to maintain barrels containing hazardous materials upright, metal hazardous material storage facilities are presently constructed with floors that are generally horizontal or flat. This can be a disadvantage as the leaked hazardous material tends to remain in the vicinity of the barrel. Therefore, to detect such a leak, a sensor must be located at each location where a barrel may be stored within the facility. Use of multiple sensors can be expensive, both to install and maintain. To reduce the need for multiple sensors, storage facilities have been designed with an upper floor with openings therethrough, e.g., a grating and a sloped lower floor. Any leaked hazardous material tends to fall through the upper floor and, in the case of liquids and heavier than air gases or vapor, gather at the low point of the lower floor. Thus, a limited number of liquid and/or vapor sensors may be placed adjacent to the low point of the lower floor and still detect a liquid leak from any barrel. These systems, however, have two disadvantages. First, such systems may not detect a small leak that does not have a sufficient volume to reach the sensor. That is, a small volume of leaked hazardous material may merely wet the sloped floor, but not spread to the trench or sensor. Second, certain systems may not include sensors to detect hazardous vapor.
Because hazardous liquids and solids materials, upon evaporation or sublimation, may create hazardous vapors or explosive vapors, a hazardous storage facility must also provide adequate ventilation. Typically, a continually running vent system powered by one or more fan assemblies replaces the air within the storage facility multiple times within an hour. Sensors structured to detect hazardous vapors, hereinafter “vapor sensors,” are typically located within the ventilation system near the exhaust duct. While such a ventilation system is desirable for maintaining a safe atmosphere within the storage facility, the rapid exchange of air creates difficulties in detecting hazardous vapor. It is axiomatic that a sensor must be exposed to a detectable quantity of vapor before it may provide a warning of the vapor's presence. However, in a storage facility where the air is replaced rapidly, a hazardous vapor may not collect in a detectable quantity. This is especially true where the hazardous material has fallen to the lower floor and the vents and vapor sensors are located on the roof or on the upper portion of a wall. In this configuration, any hazardous vapor originating on the floor is diluted in air from the upper area of the facility prior to being passed through the vent and the vapor sensors. Thus, a leaking container may exist and not be detected by the sensor system. As with liquid sensors, use of multiple vapor sensors disposed throughout the facility can be expensive, both to install and maintain. Additionally, because the prior art systems tended to mix the hazardous vapor with the air in the facility prior to venting to the atmosphere, workers within the storage facility may be exposed to the hazardous vapor.
A disadvantage of the prior art hazardous vapor detection systems was that the air flow through the facility had to be strictly controlled. That is, the prior art systems typically had an intake fan and an exhaust fan. The two fans were located at opposite sides of the facility. Thus, a cross flow was created. One problem with the cross flow pattern was that the pattern could be easily disrupted by a breach in the facility walls, e.g., an open door. That is, if a door adjacent to the exhaust fan was left ajar, air would flow in through the door and immediately be exhausted through the exhaust fan. This could allow a dangerous amount of hazardous vapors to accumulate in the facility that would remain undetected as the hazardous vapors never reached the sensor adjacent to the exhaust fan.
There is, therefore, a need for a vapor sensor system for a hazardous material storage facility structured to collect air from locations prone to collecting leaked hazardous material.
There is a further need for a vapor sensor system for a hazardous material storage facility that is structured to draw hazardous vapors away from the portion of the facility that may be occupied by humans.
There is a further need for a hazardous material storage facility which provides a device structured to removing hazardous vapor therefrom while limiting the amount of hazardous vapor mixed with the hazardous material storage facility air.